Polyether-Based Film Material

ABSTRACT

The invention pertains to high-molecular compound-based composite materials using carbon and can be used for anodes of electrolytic capacitors made on the elastic dielectric film base with current-carrying coating. 
     Polyester-base film material chiefly of polyethylene terephthalate has nanodimensional metal coating. 
     New is that a diamond-like layer 5-50 nm thick is placed between the modified surface of the polyester base and metal coating and a sponge metal layer 0.5-20 μm thick is made on the metal coating surface, said sponge metal layer has a surface development factor within the range of 80-400 and the diamond-like nanolayer is sp3-hybridization of amorphous carbon atoms gas-phase deposited in vacuum by means of a ion-plasmous source. 
     The proposed film material with a wide range of electrophysical properties is intended to be used in microelectronics and radio engineering as versatile constructional material. In particular, when used as an anode of the electrolytic capacitor its specific electric capacity is increased due to increased working voltages and adhesion between highly developed surfaces of functional nanolayers of film coating.

The invention relates to composite materials on basis of high-molecular carbon-based substances, and can be used for anodes of electrolytic capacitors made on basis of elastic film of dielectric with current-carrying coating.

Level of the given field of technique is characterized by film electrodes based on polymer with two-sided electric layer of coating in which energy is accumulated in the thin, of molecular dimensions, layer of volume charge at the border electrode/electrolyte while external voltage is applied lower than decomposition potential of electrolyte (liquid or solid) (see, for example, Shurygina V., Super Capacitors, Magazine “Electronics: Science, Technology, Business”. 2003, No. 3, page 20).

Considering number of coincident characteristics, the most similar analogue to the offered is composite material 11-14 micro-microns thick, made on basis of polyethylene terephtalate film with two-sided metal coating of nanodimensional layers, described in Patent RU 2210389, A 61L 15/00, 2002.

The known metallized film material is made under the roll technology in process of feeding of the polyester film through vacuum chamber, by means of deposition of metal from vapor phase with the aid of magnetron.

The disadvantage of this material is low adhesion of polyethylene terephtalate to metals, therefore the deposited layer of the amorphous metal is to be compacted by additional annealing to get the necessary granularity under high homogeneity level, which is labor-intensive, and does not technologically provide for stability of destination indices in the length of the metallized film.

It is not presented itself possible to use this material in a practical manner as the anode of electrolytic capacitor due to its unsatisfactory electro-physical characteristics.

The task the present invention is aimed to solve is improvement of the composite film material of polyester base with current-carrying metal coating, to improve electro-physical characteristics adapted to conditions of their industrial application in electrolytic capacitors as anodes.

The required technical result is achieved by the fact that in the known film material of polyester base, predominantly made from polyethylene terephtalate, with nanodimensional metal coating, in accordance with the invention, there between the modified surface of the polyester base and metal coating the diamond-like layer of 5-50 nm is located, and on the surface of the metal coating there is made porous metal layer of 0.5-20 microns, which has factor of surface development in the range of 80-400, at that the diamond-like layer represents itself sp3-hybridization of atoms of amorphous carbon deposited in vacuum from gaseous phase by means of ion-plasmous source, and at that the polyester base is preliminarily modified by surface geometry and through pores of size of 0.2-6 microns.

In process of using of the new multi-layer film structure as the anode of electrolytic capacitor, the distinguishing characters provided for the improvement of the principal destination indices: increase of the specific electric capacitance and mechanical properties owing to porosity of sponge metal on the surface in combination with high adhesion between functional layers of the coating on the modified, highly developed surface of the base.

The choice of the polyethylene terephtalate film for the basis of the material is determined by its service characteristics (high physical-mechanical and insulating properties, thermal resistance, chemical stability, as well as resistance to galling, mashing, influence of light and microorganisms) which, in combination with the efficient roll technology of production of metal-film anodes, determine relatively low use value of the electrolytic capacitors with their power range breadth to the maximum.

The modification of the surface of the polyethylene terephtalate film made by means of ion treatment in atmosphere of mixture of nitrogen and oxygen (air), destroying carbonyl groups, changes its relief and increases roughness, and in that way improves the cohesion with applied coatings.

The modification of the surface of the polyester base creates the “information matrix”, that is highly developed profile of the surface of the film base, which determines the geometry and interconnection form of the structure of the deposited coating, and consequently the electro-physical properties of the material on the whole.

The modification of the surface of the polyester base by geometrical relief increases the strength of cohesion with the functional coating, whereas the through pores provide for the geometrical ring-shaped locking of the two-sided metal coating.

The ion treatment of the polyester film surface creates highly developed geometrical relief and saturates it with excess energy, and in that way provides for the multiple increase of the adhesion to the functional coating made from amorphous carbon.

The placement of the diamond-like layer 5-50 nm thick between the corrugated polyester base and the nanodimensional metal coating provides for:

-   -   In the first place, barrier for the active constituents of the         base polymer, which prevents their diffusion into the coating,         and thus stabilizes the electro-physical characteristics of the         film;     -   In the second place, the increase of adhesion of layers in this         composite structure up to values more than 1.5 Newton/mm, as         well as the increase of critical value of voltage breakdown         (field intensity) by 1.5-1.7 times, which allows to increase         substantially the rated parameters of the metal-film capacitors         as well as their serviceability.

The diamond-like nanodimensional coating possesses of semi-conducting properties and increases the dielectric permeability of the material.

The specificity of carbon atom consists in its capability for forming of strong inter-atomic bonding characterized by different type of hybridized electron orbital. The ties in diamond lattice are characterized by sp3-hybridized state of amorphous carbon, whereas sp2-hybridization complies with graphite and sp-hybridization complies with carbine.

The diamond-like layer less than 5 nm thick does not have a noticeable influence upon the improvement of the electro-physical properties of the film material, and than this layer is more than 50 nm thick the film elasticity is reducing, and there is no increase of its strength.

The adhesion of the two-sided current-carrying metal coating for the most part is provided for by Van der Waals forces as well as owing to the forming of coating at the border of partition of the highly developed relief.

Production of the current-carrying coating in the form of porous metal layer 0.5-20 microns thick increases the film electrode capacity, at that its cross-oriented structure improves the sorption properties while interacting with liquid electrolyte and allows to increase iteratively the contact surface of metal-film anode of electrolytic capacitor and to reduce distinctly its external dimensions.

Than factor of development of porous metal coating surface is less than 80, the electric capacitance of the film anode is not sufficient for the industrial use.

Than the factor of development of this functional surface is more than 400, there are forming pores of too small dimensions, which are not filled in with electrolyte, and therefore the anode capacity is not increasing.

The pores of size less than 0.2 microns in the material polyester base do not substantially influence upon the adhesion with functional nanodimensional coating. While the ionic-plasmous deposition of the coating metal, the pores are being becoming dusty and practically dwindle, which has a negative influence upon the sorption properties of the material and reduces the electric capacitance of the anode made from it.

The size of pores more than 6 microns is not economically feasible while the bearing strength of the base is being lost in the roll technology of the coating formation.

Therefore, each of the essential features is necessary, and their summation is enough to achieve the quality newness not inherent in the features taken separately, that is, while solving of the technical problem put by the invention there the effect of the features sum is received, and not the sum of their effects.

The main point of the invention is illustrated by the route technology of the production of the offered material.

In the invention there is for the first time worked out the physical model of the formation of the high-adhesion layer of metal to the polymer surface, and the offered structure of metal-film anode for electrolytic capacitor is experimentally realized.

The surface of the polyethylene terephtalate film is being sequentially treated in vacuum chambers equipped with lockage devices, in the dynamics of rewind at the speed sufficient for practical realization in production.

Preliminarily the surface of the film base of the composite material is being treated in the atmosphere of mixture of nitrogen and oxygen by means of ionic emitter under anode acceleration voltage of 2 kV, discharge current of 2 A, solenoid current of 200 mA, and as a result the development of the relief of the polyester film surface is provided for.

The received relief of the surface has been estimated by means of scanning probe microscope “FemtoScan” in atom-power regime and other well-known methods to determine roughness, area of the real and geometrical surface, correlation of which determines the development factor.

There in the film base, by means of gas-discharge plasma and ion beam, the riffles 0.2-3 microns deep or pores of size 0.2-6 microns are formed, of total volume of 10-60%, at that ⅓-⅕ part of the pores is made through, achieving the factor of the base surface development to be in the range of 8-40.

After that in atmosphere of cyclohexane vapor there the ion-stimulated deposition of nanodimensional (10-50 nm) coating from amorphous carbon of sp3-hybridization condition is made, and as a result the modified film material acquires properties of electrets.

The laying of this coating is made by means of ion-plasmous source

-4-0-15 from cyclohexane vapor under anode acceleration voltage of 3 kV, discharge current of 200 mA, solenoid coil current of 2 A.

After the nanodimensional diamond-like coating is laid upon the base film surface, dielectric permeability is increased, and the potential barrier of transfer to metal-dielectric is formed. The increase of dielectric permeability is connected with the increase of volumetric electro-conductivity of the film.

The multiple development of the surface of interaction of the polyester base with this technological nanolayer of the coating has noticeably increased the adhesion, provided for their firm cohesion into the integrated structure, onto which the current-carrying layer of metal, copper or aluminum is to be further laid.

The nanodimesional coating on basis of carbon, deposited onto the modified surface of the polyester film, has a substantial influence upon the process of the film disruption, leading to the increase of the critical value of the electric field (intensity of the field where the disruption takes place) by 1.5-1.7 times with the increase of the coating thickness from 5 to 50 nm correspondingly. For its turn it allows to considerably increase the nominal parameters and serviceability of the metal-film capacitors.

Then the current-carrying metal coating 25-250 nm thick is laid onto the formed diamond-like nanolayer by means of magnetron.

As a result the achieved adhesion of metal to polymer is 14-20 times higher than that of the analogues known in the engineering.

At that the metal layer hermetically seals up from two sides the pores of the base where the vacuum space remains, and the vacuum space during the exploitation of anodes functions as rivets in the material, and in addition it mechanically presses the metal coating to the polymeric film base.

When the film polyester base remains permeable, that is the large through pores are covered by the layer of deposited metal from within, and on the end surfaces are opened, there in the polymeric base the closed circular layers of the coating metal coherent with the base are formed, and this is to provide for the geometrical locking of the current-carrying layer, which is physically adjoined to the modified film and practically is not exposed during exploitation.

There the following regime of metallization of the modified film by the source of magnetron type has been chosen: discharge voltage—600 V, discharge current—10 A, pressure in the chamber filled with argon, comes to 0.001 torr. The travel speed of tape along the plant came to 0.3 m/min.

Then this bearing metal layer is additionally deposited over with the functional layer of porous metal 0.5-20 microns thick, which under the influence of the “information matrix” of the modified base is formed in the form of pyramidal structure with the factor of the surface development in the range of 80-400.

The technological regimes of production of the offered composite multi-layer material with different combinations of the structural layers with different geometrical parameters are worked through in the experimental plant and optimized in accordance with the data of the investigations of the electro-physical properties of anodes, according to the operating conditions.

The offered film material with wide range of the electro-physical properties is meant for using in microelectronics and radio engineering in the capacity of the universal constructional material.

High values of the electric charge, stable at temperatures up to 200° C. allow using of the modified polyester film in the capacity of the cheaper sensing element of the electro-mechanical and electro-acoustic transformers. The sensitivity of such a transformer is identical to the sensitivity of device with magnetic ferroelectrics made from polyvinyl den-fluoride, and its cost is considerably lower.

The modified surface of the polyester film with the diamond-like coating is bactericidal, and this is conductive to reduction of the speed of behavior of processes of biological corrosion during the exploitation of electronics in the extreme conditions.

The material under the invention may be used in particular in the capacity of secondary filter for different yielding materials, liquids, aerosols and gases.

The comparative analysis of the offered technical solution, carried out with the ascertained analogues of the technical level from which the invention is not evidently resulted for the technologist of production of semi-conductors, has shown that the invention is not known, and taking into consideration the possibility of the industrial full-scale production of the metal-film anodes for electrolytic capacitors it is possible to draw a conclusion about its correspondence to the patent-ability criteria.

The invention relates to composite materials on basis of high-molecular substances with using of carbon and can be used for anodes of electrolytic capacitors, made on basis of elastic film of dielectric with current-carrying coating.

The polyester based film material, predominantly made from polyethylene terephtalate, and has nanodimensional metal coating.

The new is that between the modified surface of the polyester base and the metal coating there is located the diamond-like layer 5-50 nm thick, and there on the surface of the metal coating the porous metal layer 0.5-20 microns thick is made with the factor of surface development in the range of 80-400, at that the diamond-like nanolayer represents sp3-hybridization of atoms of amorphous carbon precipitated in vacuum from gaseous phase by means of ion-plasmous source.

The offered film material with wide range of the electro-physical properties is meant for using in microelectronics and radio engineering in the capacity of the universal constructional material. In particular, while using as the anode of electrolytic capacitor it is provided for the increase of its specific electrical capacitance due to the increase of the working voltages and adhesion between the highly developed surfaces of the functional nanolayers of the film coating. 

1. Film material based on polyester, predominantly made from polyethylene terephtalate, with metal coating, different from the others because of the fact, that between modified surface of the polyester base resulted in the development of its relief by means of ion radiator in the mixture of oxygen & nitrogen and the metal coating there is located diamond-like adhesive layer 5-50 nm thick which bears barrier function, and there on the surface of the metal coating there is made porous layer of metal.
 2. Film material under item 1, different from the others because of the fact, that diamond-like nanodimensional layer represents itself sp3-hybridization of atoms of amorphous carbon deposited in vacuum from gaseous phase, particularly in the atmosphere of cyclohexane vapor, with ion stimulation by means of ion-plasmous source.
 3. Film material under items 1, different from the others because of the fact, that porous metal layer which has factor of surface development in the range of 80-400 and is of 0.5-20 microns thick.
 4. Film material under items 1, different from the others because of the fact, that polyester base is preliminary modified by surface riffles and/or by pores of size 0.2-6 microns and of total volume of 10-60%.
 5. Film material under items 4, different from the others because of the fact that riffles are formed 10-30 nanometers deep.
 6. Film material under items 4, different from the others because of the fact that ⅓-⅕ part of the pores is made through. 